Dry eye, also known as keratoconjunctivitis sicca, is a common ophthalmological disorder affecting millions of Americans. The condition is particularly widespread among post-menopausal women due to hormonal changes following the cessation of fertility. It is one of the most common of human eye diseases and is generally treated through the topical delivery of a variety of therapeutic agents.
Dry eye may afflict an individual in varying severity. In mild cases, a patient may experience burning, a feeling of dryness, and persistent irritation when debris lodge between the eye lid and the eye surface. In severe cases, vision can be substantially impaired.
Although it appears that dry eye can result from a number of unrelated pathogenic causes, all presentations of the syndrome have in common the breakdown of the pre-ocular tear film. This breakdown results in dehydration of the exposed cornea and conjunctiva and many of symptoms associated with dry eye.
Eye care practitioners have taken several approaches to the treatment of dry eye. One common approach has been to supplement and stabilize the preocular tear film using artificial tears. Another approach has been the use of ocular inserts that function to provide a tear substitute or to stimulate endogenous tears.
Examples of the tear substitution approach include the use of buffered, isotonic saline solutions, and aqueous solutions containing water soluble polymers that render the solutions more viscous and thus less easily shed by the eye. Tear reconstitution is also attempted by providing one or more components of the tear film such as phospholipids. Another recent approach involves the provision of lubricating substances in lieu of artificial tears. Other treatments involve the use of hormones, such a conjugated estrogens, to treat dry eye in post-menopausal women.
Although these approaches have met with some success, there remains problems in the treatment of dry eye. The use of tear substitutes, for example, generally requires many repeated applications over the course of a patient's waking hours. It is not uncommon for a patient to have to apply artificial tear solution ten to twenty times over the course of the day. Such dosing is cumbersome and time consuming, increases the exposure of the eye to preservative agents present in many artificial tears.
Similarly, ocular inserts are often difficult to insert and uncomfortable when used as intended. Further, as foreign bodies, ocular inserts pose a risk of acting as a vector for infectious organisms.
Therefore, there remains a need for a safe and effective treatment for dry eye. Ideally, the treatment should be capable of treating dry eye due to a variety of causes. Further, the treatment should not require the application of a drug on a very frequent basis, and should be easy to use. Also, the treatment should not cause discomfort itself and should cause minimal blurring, if any.